Sewage dewatering process and equipment

ABSTRACT

A process of dewatering primary-treated sewage which includes mixing the sewage with a coagulant or flocculant aid, usually activated polymer. The sewage is then mixed and flocculated at conditions which involve extensive mixing turbulence of the sewage and whereby part of the sewage is recycled so as to be again subjected to such mixing and flocculating. Flocks form the solid particles in the sewage. The pH of the sewage is chemically adjusted into the basic pH range or to a higher basic pH. The sewage is applied to a sand bed whereby the flocculated solids in the sewage are separated from the liquid in the sewage, by collecting on the top of the sand bed. The flocculated solids located on the top of the sand bed are air dried. The dried flocculated solids are removed from the top of the sand bed.

This is a divisional application of Ser. No. 08/419,289, filed on Apr.10, 1995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a sewage dewatering process and equipment tocarry out the process.

2. Background Art

Sewage is composed of the liquid and water-carried wastes fromresidences, commercial buildings, industrial plants, and institutions,together with any groundwater, surface water and storm water which maybe present. The terms "wastewater" and "sewage" are sometimes usedinterchangeably herein.

The composition of sewage depends on its origin and the volume of waterin which the wastes are carried. Sewage which originates entirely fromresidential communities is made up of excreta, bathing and washingwater, and kitchen wastes. Other wastes can be present fromrural/agricultural sources and/or industrial or commercialestablishments.

Modern sewage treatment is generally divided into three phases: primary,secondary and tertiary. Each of these steps produces sludge, which canbe disposed of or used for various purposes.

Primary treatment, or plain sedimentation, removes only the settleablesolids from sewage. A modern system for primary treatment entailscollecting the sewage, conveying it to a central point for treatment,using both screens to remove large objects and grit chambers to removegrit, and using primary sedimentation tanks to remove the suspendedsettleable solids. This type of system produces about one third of agallon of wet sludge per person per day, and facilities for handling anddisposing of the sludge are also needed. Primary treatment reduces theconcentration of suspended solids by about 60 percent and reduces theBOD (biochemical oxygen demand) by about 35 percent.

Secondary treatment involves the addition of a biological treatmentphase following plain sedimentation. At best, this treatment removesabout 85 to 95 percent of the organic matter in sewage. It has littleeffect on dissolved materials or on the nutrients that stimulate thegrowth of algae in the receiving waters. It also discharges all of thenutrients and dissolved solids, as well as any contaminants which may beadded to the water by industrial plants.

There are two basic methods of often used in modern secondary treatment,that is, the trickling filter and the activated-sludge processes. Insmall communities, secondary treatment is sometimes accomplished byeither the trickling-filter method or the contact bed method, butusually used is the sand filter method. In larger communities, secondarytreatment is generally accomplished by the activated-sludge process.

Sand filters are beds of fine sand, usually 3 feet (1 meter) deep,through which the sewage slowly seeps. As it seeps through the sand, theorganic matter is decomposed and stabilized by the microorganisms in thesewage. Sand filters require about 4 acres (1.6 hectares) of sand bedsfor each thousand people. Because of this large space requirement, sandbeds have obvious disadvantages. Also, the time required for the sludgeto be formed and dried usually takes weeks. This long drying time meansthat large surface areas of sand beds have to be used to achieve dryingwith the attendant large cost of constructing, operating and maintainingthe sand beds. Rain adds time to the drying function of sand beds, sincethe sand beds usually are without any roof or other top covering.Covered sand beds require less area than do uncovered beds but stilltake weeks to achieve drying and have a higher construction cost.Nowadays, about 90 percent of smaller municipalities use sand beds todewater sewage coming from primary treatment units. The main purpose ofsand beds is the reduction of the water content in the primary-treatedsewage.

A contact bed, composed of many layers of stone, slate or other inertmaterial, provides a relatively large surface area for the growth ofmicroorganisms. It operates on a fill-and-draw basis, and the organicmatter delivered during the fill period is decomposed by themicroorganisms on the bed. The oxygen required by the microorganisms isprovided during the resting period, when the bed is exposed to the air.

In the trickling filter system, the sewage is applied to the filterthrough rotary distributors and, then, is allowed to trickle down overlarge stone or plastic beds that are covered with microorganisms. Thebeds are not submerged and, thus, air can reach the organisms at alltimes. The area requirements for trickling filters are about 5 to 50acres (2 to 20 hectares) per million people.

In the activated-sludge process, heavy concentrations of aerobicmicroorganisms, called biological floc or activated sludge, aresuspended in the liquid either by agitation which is provided by airwhich is bubbled into the tank or by mechanical aerators. Finalsedimentation tanks are needed to separate the floc material from theflowing liquid. Most of the biologically active sludge, then, is thenreturned to the aeration tank with which to treat the incoming water.The high concentration of active microorganisms which can be maintainedin the aeration tank permits the size of the treatment plant to berelatively small, about 1 to 5 acres (0.1 to 2 hectares) per millionpopulation.

Tertiary treatment is designed for use in areas either where the degreeof treatment must be more than 85 to 95 percent or where the sewage,after treatment, is reused. It is mainly intended to further clean orpolish secondary treatment plant effluents by removing additionalsuspended material and by lowering the BOD, generally by filtration.This polishing, however, has little impact on the dissolved solids,including the nutrients, synthetic organic chemicals, and heavy metals.To eliminate these constituents of sewage, other methods of treatmenthave been devised. These processes include coagulation andsedimentation, precipitation, adsorption on activated carbon or otheradsorbents, foam separation, electrodialysis, reverse osmosis, ionexchange and distillation.

Sludge is the semiliquid mass removed from the liquid flow of sewage.Sludge will vary in amount and characteristics with the characteristicsof sewage and plant operation. Sludge from primary treatment is composedof solids usually having a 95 percent moisture content. The accumulatedsolid materials, or sludge, from sewage treatment processes amount to 50to 70 pounds (22 to 31 kg) per person per year in the dry state or aboutone ton (0.9 metric ton) per year in the wet state. Sludge is highlycapable of becoming putrid, and can, itself, be a major pollutant if itis not biologically stabilized and disposed of in a suitable manner.Biological stabilization may be accomplished by either aerobic oranaerobic digestion. After digestion, sludge-drying beds are usuallyused.

In modern sewage treatment plants, mechanical dewatering of sludge byvacuum filters, centrifuges, or other devices is becoming widespread.The dewatered sludge, then, may be heat-dried, if it is to be reclaimed,or it may be incinerated. In large communities where large amounts ofsludge are produced, mechanical dewatering and incineration are commonlypracticed. But there are many smaller communities, rural areas, etc.,which have economic constraints and which use the sand bed method todewater sewage. There is a great need to make the sand bed method moreeconomical by reducing the time for drying waste material (sludge) fromthe primary-treated sewage effluent and by reducing the time for dryingthe sludge. Reduced drying time would allow reduction of the size of thesand beds needed.

Early sludge treatment schemes included plain sedimentation, followed bychemical precipitation or sedimentation aided by flocculation chemicals.Chemical precipitation fell into disuse, but may be making a comeback.Nowadays, chemicals are often added to the sewage to promote thecoagulation of the finer suspended solids, so that these solids becomeheavy enough to settle in sedimentation in the primary treatment stage.Typical chemical coagulants in the flocculation of sewage are alum,polymers, ferric sulfate, ferric chloride and lime.

Chlorine is often used to minimize odors from sedimentation tanks and inthe final effluent as a disinfectant.

U.S. Pat. No. 5,248,416 (Howard) discloses a sewage treatment systemwhich presents a main flow line and a recirculating line, the former forfloc which has appreciated in size due to the addition of a polymer andto passage through an area of agitation/turbulence, and the latter forthe return of small sized floc to the agitator/turbulence area for sizeincrease. The passageways of the system include movable flaps whichserve recirculation purposes, and a ledge or flutter for currentcreation and floc build-up. Raw liquid sewage enters the system, whereasthe outlet leads to a belt press and/or a dry bed to cake the resultingsludge. More specifically, the apparatus for flocculating fluidscontaining suspended solids comprises conduit means for conducting thefluid to an outlet in the conduit means. There is means introducing aflock-producing agent into the fluid in the conduit means, a verticaldrop in the conduit means downstream from the means introducing theflock-producing agent, and a movable mounted ledge means in the verticaldrop which serves to increase turbulence and to increase the size ofaccumulating floc in the fluid. There is a vertical rise in said conduitmeans, downstream from the vertical drop leading to the outlet. Theconduit means includes means connecting the vertical drop to thevertical rise, and there are circulation passageway means connecting thevertical rise to the vertical drop for recirculating smaller size flockto the vertical drop.

In Howard, it is said that a particular feature is that no mixerequipment is required. Polymers are injected into the raw sewage,causing water to separate from the raw sewage during the procedure,resulting in floc build-up. The latter is caused when the polymers begindissolving with the result that a film of concentrated polymer solutionbuilds up about the polymer particles, forming aggregates oragglomerations, identified as "flocks". Turbulence is a key factor,where such is said to be accomplished through a ledge (which flutters)located in the vertical drop conduit and a series of movable flapsdisposed within the recirculating conduit. The singular stated purposeof the Howard scheme is to create flock, i.e., solids with a minimum ofwater content, through separation. Restated otherwise, the Howardscheme, through turbulence or tumbler-mixer action, is said to createadditional floc (of a larger size) which goes to output, whereas smallerfloc is caused to recirculate said increase, thereby, in size forrepeated passage to output.

BROAD DESCRIPTION OF THE INVENTION

An object of the invention is to overcome the above-mentioneddisadvantages and problems of the prior art sewage dewatering treatmentprocesses. Another object of the invention is to provide process-schemesand equipment whereby the size and/or number of sand bed(s) needed canbe greatly reduced. Another object of the invention is to provideprocess-schemes and equipment whereby the time to dewater sewage anddrying the sludge is greatly reduced. A further object of the inventionis to provide process-schemes and equipment whereby the dried sludgeobtained from dewatered sewage has a greatly reduced water content.Another object of the invention is to provide a mixer-flocculator whichcan be used to flocculate particles dissolved in a liquid. Anotherobject of the invention is to provide a pneumatic deliquiding unit whichcan be used to remove liquid from a solution containing solid particles.Another object is to provide equipment for removing a layer of solidmaterial in particulate form from on top of a layer of solid particulatematerial such as sand. Other objects and advantages of the invention areset out herein or are obvious herefrom to one skilled in the art. thesewage dewatering treatment process of the invention.

The invention involves a process-scheme for dewatering sewage, usuallypreviously subjected to primary treatment, to obtain dried sludge.Solids are dissolved, suspended, etc., in the liquid sewage. The processincludes: (a) mixing the sewage with a coagulant or flocculant aid; (b)mixing and flocculating the sewage from step (a) at conditions whichinvolve extensive mixing turbulence of the sewage and whereby part ofthe sewage is recycled so as to be again subjected to such mixing andflocculating, flocks being formed from the solid particles in thesewage; (c) chemically adjusting the pH of the sewage from step (b) intothe basic pH range or to a higher basic pH; (d) applying the sewage fromstep (c) to a sand bed whereby the flocculated solids in the sewage fromstep (c) are separated from the liquid in sewage from step (c), bycollecting on the top of the sand bed, and drying the flocculated solidslocated on the top of the sand bed; and (e) removing the driedflocculated solids from the top of the sand bed. The sewage is usuallysupplied to step (a) under sufficient pressure/head (by means of a pumpor line pressure) to travel completely through the process sequencewithout the need for an auxiliary pump(s) can be used if desired.

Dewatering sludge at wastewater treatment plants has traditionally beena major operational concern. Most large operations use mechanical filterpresses to efficiently dewater their sludge. For smaller operations thisequipment is too expensive and too large for their needs. Therefore,small facilities rely on said filter drying beds for sludge dewatering.This is an excellent method to process sludge; however, most beds weredesigned without inline dewatering (liquid-solid-separation) or an easyand automated way to remove dried sludge. Expensive time-consumingmanual labor has been a tremendous burden to plant operation. Theinvention process and equipment solves the old sludge bed problems. Withsimple and easy modifications of existing beds, old non-productive bedscan be upgraded to good dewatering devices. The invention process andequipment allows any wastewater treatment plants to change their sludgebuild-up problem to a modern and cost effective method to dewater, dryand remove sludge.

The invention process also includes an optional step of dewatering thesewage using an inline pneumatic dewatering tube between steps (a) and(b) or (b) and (c) or (c) and (d), or before step (a). Use of thevertically-situated pneumatic dewatering device or tube involvesconducting the sewage into the central tube-shaped filter where solidsin the sewage are caught on the filter and some of the water in thesewage passes through the filter. Air under pressure is blown againstthe outer surface of the filter to dislodge the solids collected on theinner surface of the filter. The blowing air sources are alternated inon-off sequences in order to continuously provide regions of the filterfor the water to come through unimpeded by blowing pressurized air. Thethickened or concentrated sewage passes on to the next process step oroperation.

The invention also involves the processes for dewatering primary-treatedsewage which comprised (1) above-noted steps (a). (b) and (c), or (2)above-noted steps (a) and (b), or (3) above-noted steps (b) and (c), or(4) above-noted step (b).

The first step/stage in the invention process-scheme uses an inlinepolymer mixing-feeding (injection) system to incorporate activatedpolymer into the sewage flow line. The inline polymer preparation systemeliminates this need for batching tanks, mixers and polymer transferpumps. The inline polymer system can be a conventional one or preferablyis the novel inline polymer mixing-feeding system of the invention. Thenovel inline polymer system (chemical pump) of the invention activatesprecise amounts of neat polymer and water, then meters the fullyactivated stock solution to the point of use without the need oftransfer pumps. The benefits achieved by the novel inline polymer systeminclude:

(A) Fully automated--any polymer--any application;

(B) Full polymer activation and little or no waste;

(C) Reduces labor and maintenance costs;

(D) Saves space--is portable; and

(E) Simplifies operation and improves safety.

The polymer mixing-feeding (injecting) system is an integrated equipmentpackage which automatically meters, activates, dilutes and feeds liquidpolymer and water. Concentrated polymer and water are blended in acomplete high energy chamber.

The prepared solution (neat polymer and water) exits the originalchamber through the top of the vessel. It shall then re-enters an outerretention chamber and exits the chamber at the bottom of the vessel. Around access plate is fabricated in the bottom of the primary chamberfor repair and service. The chamber can be constructed of polyvinylchlorides, stainless steel or any other suitable material. The polymeris injected into the chamber through a tube passed through the top ofthe chamber. The tube is designed to be adjustable in length givingvariations in depth or placing the polymer closer to the aspirator ormixing energy. At the end of the tube, a spring loaded check valveallows polymer to spray into the mixing area in a thin filming process.Energy for polymer activation is created by 5/8 inch or any sizestainless steel hollow shaft which at the end of the shaft is apolyvinyl chloride or stainless steel 4-way aspirator. Turning at 3,450rpm a tremendous vacuum occurs drawing free air down the shaft into thechamber. This process causes high energy mixing. The stainless steelshaft is driven by a hollow core motor. The system activates the polymerand meters the activated polymer--water solution to the point of usewithout the need of transfer pumps.

The motor and shaft are attached by a coupler. The 5/8 inch or any sizeshaft with aspirator is placed inside the chamber and that chamber ismade water tight with exterior mechanical seals. Inline check and ballvalves are installed on the top or inlet side of the motor. These valvescan regulate the amount of air passed through the shaft to the mixingchamber. The one way directional flow check valve is used to preventliquid from exiting through the aspirator and shaft when the motor is inthe off position. The mixer has a brass solenoid valve for on/offcontrol of dilution water supply, and a rotameter-type flow indicatorequipped with integral rate-adjusting valve. The flow indicator ismachined acrylic and has valve stop and guided float. Water flow rate isadjustable 0 to 500 USGPH. Water supply input and stock solution outputfittings are 0 to 500 FNPT. The drive motor of the unit is powered by a2500 watt generator producing 12OV-15 amps. The generator is mounted tothe trailer and becomes a permanent fixture of the transportable system.

The polymer is an emulsification of long chain organic polymer in oil.The water and mixing opens up or uncoils the polymer to expose chargesites in the polymer chain.

Coagulants or flocculants, such as, alum, ferric sulfate, ferricsulfate, ferric chloride and lime, can be used in place of the activatedpolymer in the sewage flow line to coagulate or flocculate the solids inthe sewage. These coagulants or flocculants cause formation of aninsoluble precipitate which adsorbs colloidal and suspended solids.

The second step/stage in the invention process-scheme uses an inlinemixing flocculator. A novel inline mixing-flocculating device is used toenhance the chemically induced liquid-solids separation in the sludgedewatering process utilized at most wastewater treatment plants. Theflocculator is used in any type of mechanical dewatering scheme thatuses a chemical as a coagulant or flocculant aid. The overall output andefficiency of the dewatering process is greatly increased by thethoroughness of the flocculating process. Prior art sludge productionnormally is 14,000 to 16,000 gallons of dewatered sludge per gallon ofpolymer; the invention mixer-flocculator unit provides a reduction of 40to 60 percent in polymer consumption. The benefits achieved by theinline mixing-flocculating device include:

(A) Increases sludge production;

(B) Decreases polymer usage;

(C) Increases drying bed holding capacity; and

(D) Decreases sludge drying time.

The prepared activated polymer exits the polymer preparation system andis passed into the mixer-flocculator unit. Preferably, themixer-flocculator unit has multiple injector ports at the influent endof the mixer through which the activated polymer solution can beinjected into the liquid-sludge slurry flow stream. The activatedpolymer and sludge is quickly yet gently mixed by baffling energydispersing action. The mixing action promotes large floc growth. Aportion of the flocculated sludge is re-circulated into the influentstream by a pressure drop zone to advance and increase the efficiency ofthe mixing-flocculating process.

The mixer-flocculator unit includes, in the down section above therecycle pipe, an adjustable, nonflexible baffleplate which is positionedat an angle. The adjustment can be controlled by hand adjustment meansor electrically operated means. The baffleplate restricts the flow inthe down pipe by about 50 to about 80 percent, thus increasing theoriginal flow velocity by as much as 600 percent. With a lower sewageflow rate, a thinner throat is usually used; with a higher flow rate,normally a wider throat is provided with the adjustable baffle plate.Then, the pattern of flow is fanned in one direction. Thereafter, it isoppositely directed and fanned by a fixed baffle which restricts about40 percent of the vessel's size. Then, the flow is directed into a 45degree round angle causing the flow to turn and pass under and over andunder fixed baffles in a serpentine flow pattern, which is reducing thevessel's velocity. The flow, then, enters a 45 degree round angle whichcauses the flow to move in a spiraling pattern which, then, comes incontact with a fixed baffle. As the flow exits the mixer-flocculatorunit, it passes a horizontal pipe which causes a portion of the flow todivert through this line by the pressure drop caused by the adjustableinlet baffle. The bypass velocity may be increased if the size of thepipe is increased and with baffleplate adjustments.

As the liquid/solids content exits the inline mixer-flocculator, anelectronic driven diaphragm pump or gear driven pump pumps liquidcaustic into the discharge line of the mixer-flocculating system.

Benefits of use of the mixer-flocculator system described herein arenumerous. The better the mixing, the better the flocculation. It is anew type of in-line mixing-flocculating system used to enhance thechemically induced liquid-solids separation in the sludge dewateringprocess utilized at most wastewater treatment plants. The mixer iscapable of being utilized in any type of mechanical dewatering schemewhich uses a chemical as a coagulant or flocculant aid. Typically,polymers are used at most wastewater treatment plants and are fullyactivated prior to being injected into the sludge slurry. The instantmixing-flocculating system performs the task of mixing the activatedpolymer solution with the sludge more rapidly and effectively because ofa cascading "waterfall" flow pattern with strategically placedbaffleplate, baffles and a baffled recirculating line. The mixer can beused in plants using sand drying beds, belt filter presses orcentrifuges for partial dewatering of the sludge-slurry. Themixing-flocculating system shall be capable of increasing the overalloutput and efficiency of the dewatering process. A summary of thebenefits of the use of the mixer-flocculator unit would include:increased sludge production, decreased polymer usage, increased dryingbed holding capacity, decreased sludge drying time and a unit which willnot clog and has multiple clean out ports.

The mixing-flocculating system shall consist of a single manufacturedmixing-flocculating device capable of providing a rapid mix of theactivated polymer and sludge slurry followed by a detention chamber ofsufficient volume to provide enhancement of floc growth within a singleunit. The device shall provide for partial re-circulation of previouslyflocculated sludge into the influent sludge slurry stream. Themixing-flocculating device shall be a controlled reduced velocity type.

The device preferably fabricated primarily utilizing corrosion freepolyvinyl chloride components or other art suitable material such asstainless steel. The device does not have any mechanically moving parts(except for the adjustable baffleplate) and is designed to requireminimum maintenance. The mixing device also is designed to minimizeclogging and can be self regulating or manual or electrically driven,regardless of flow, sludge characteristic or polymer dosage. Model RF8is rated at 0 to 700 gallons per minute. Model RF6 is rated at 0 to 200gallons per minute.

The mixing-flocculating system is a single manufacturedmixing-floccluating device capable of providing a rapid mix of theactivated polymer and sludge slurry followed by a detention chamber ofsufficient volume to provide enhancement of floc growth within a singleunit. The device provides for partial recirculation of previouslyflocculated sludge into the influent sludge slurry stream. Themixing-flocculating device is a reduced velocity type. The system is aninline mixing-flocculating device used to enhance the chemically inducedliquid-solids separation in the sludge dewatering process utilized atmost wastewater treatment plants. The mixing device is capable of beingutilized in any type of mechanical dewatering scheme that uses achemical as a coagulant or flocculant aid. The system performs the taskof mixing activated polymer with a 1/2 to 8 percent solids liquid-sludgeslurry rapidly and effectively. The system performs effectively inplants using sand drying beds, belt filter presses or centrifuges forpartial dewatering of the sludge slurry. The mixing-flocculating systemis capable of increasing the overall output and efficiency of thedewatering process. The system has multiple injector ports at theinfluent end of the mixer through which the activated polymer solutioncan be injected into the liquid-sludge slurry flow stream. The activatedpolymer and sludge are quickly but gently mixed by a tumbling,cascading, energy dispersing action. The mixing action promotes largerapid floc growth. A portion of the flocculated sludge is circulatedback into the influent stream to advance and increase the efficiency ofthe mixing-flocculating process.

The third step/stage in the invention process-scheme is a chemicalinduced pH adjustment of the sewage exiting the mixer-flocculatingsystem. Liquid caustic, lime or other suitable base is injected into thedischarge side of the mixer-flocculator unit and the temperature of thewater to the inline polymer system is increased, thereby increasing theliquid/solids pH balance.

As the liquid/solids content exits the inline mixer-flocculator unit, anelectronic driven diaphragm pump or gear driven pump pumps liquidcaustic or lime into the discharge line of the flocculator-mixer unit.The pH of the sludge is increased to 12 by the chemical. The pH of thesludge will remain at 12 for 72 hours, and, during this period of time,the temperature will reach 52° C. and will remain at that temperaturefor at least 12 hours. At the end of the 72 hour period during which thepH of the sludge is above 12, the sludge can then be air dried toachieve a percent solids of greater than 50 percent. The liquid causticor lime pump is present on the transportable dewatering trailer with themixer-flocculating system and the polymer feed system and, thus, iseasily transported.

The benefits achieved by this third step/stage include:

(A) Federal 503 Regulations are met;

(B) expensive sludge handling procedures are hereby deleted; and

(C) expensive ovens or automated lime distribution systems are not used.

The fourth step/stage in the invention process-scheme uses a sand (grid)cell in a sand bed used for dewatering sludge. The sand-cell is gridused to stabilize filtration media in any new or existing sand dryingbed. It is preferably manufactured of heavy-duty polyethylene.Preferably the sand grid is honeycomb or similar shaped. The fixed media(i.e., grid) is best installed in the filtration sand about six inchesbelow the surface. Under load, the sand-cell generates powerful lateralconfinement forces and sand-to-cell or stone-to-cell frictions. Thisprocess creates a bridging with high flexural strength and stiffness.The sand-cell greatly enhances the dewatering process. Plant operatorscan drive an end or front loader or tractor over the entire bed therebysignificantly reducing cleaning time and eliminating expensive manuallabor. Surface and subsurface bed stabilization is achieved using theinvention grid. This allows for 100 percent manueverability ofequipment, eliminates surface and subsurface compaction of the sandmedia and produces an excellent drainage environment. 100 percentsaturation and drainage within about 10 minutes from start to pouring ofthe sewage results from the use of the grid. The benefits achieved bythe sand-cell include:

(A) Directly supports front-end loaders or tractors allowing them todrive directly on the sludge drying bed without destroying the integrityof the filtration sand;

(B) Prevents lateral slippage or shear of the filtration media (grid);

(C) Reduction in filtration media replacement costs;

(D) Loading and cleaning time is significantly reduced;

(E) Uses standard washed sand or "P" gravel for rapid dewatering versusexpensive, conventional drying bed materials;

(F) Square foot installation cost reduced by 94 percent over fixed mediasystem; and

(G) Total maintenance costs are reduced by more than 75 percent.

This step of the invention involves use of a sand-cell media tostabilize filtration sand/media in any new or existing sand drying bed(best constructed of concrete).

A standard sand-cell section may have nominal dimensions of eight feetwide by twenty feet long by six inches deep. However, a standardsand-cell section can have any length, width and height to fully fitinto the dimensions of the sand cell in case. All of the individualsand-cells forming a sand-cell section, generally, are uniform in shapeand size. Preferably, the individual sand-cells are about 6 inches wide,6 inches long, about 6 inches deep, hexagonal in shape and, together,form a honeycomb. The honeycomb is one of the strongest, yet lightest,shapes found in nature. A standard sand-cell section can be made fromhigh-density polyethylene plastic, any other suitable plastic or resin,stainless steel, fiberglass, concrete, wood, or any other suitable metalor material, or any form of fabricated steel, preferably high-densitypolyethylene plastic.

The sand-cell media is advantageously installed in the filtration sandor stone with its top surface most preferably about six inches,preferably not more than 12 inches or less than 2 inches, below itssurface of the sand. Under load, the sand-cell media generates powerfullateral confinement forces and stone or sand to cell frictions. Thisprocess creates a bridging with high flexural strength and stiffness.

The benefits of using sand-cell media are numerous. A subsurface whichincludes sand-cell media does not compact which allows the free water topass quickly through the media. The high flexural strength and stiffnessof a subsurface which includes sand-cell media allows equipment such asend loaders to drive directly onto the entire sludge drying bed withoutdestroying the integrity of the filtration sand. This, in turn,significantly reduces the loading and cleaning time, and eliminatesexpensive manual labor. Other benefits of using the sand-cell mediadescribed herein include: lateral slippage or shear of the filtrationmedia is prevented; filtration media replacement costs are reduced;economical standard washed sand or "P" gravel for rapid dewatering canbe used (as opposed to conventional drying bed materials); square footinstallation costs are reduced by ninety-four percent over the fixedmedia system; and total maintenance costs are reduced by more thanseventy-five percent.

The fourth step of the instant invention includes an inline mixing in amixer-flocculator unit (which is part of a mixer-flocculating system) ona trailer. The purpose of having the mixer-flocculating system on atrailer is the ability to transport a complete dewatering system to asite to dewater sludge for drying bed application. In general, this sortof equipment should be transportable to prevent it from freezing andbeing damaged when exposed to the elements. Permanent installation ofthis sort of equipment in adjacent buildings is not suitable, becauseformed floc will separate and self-destruct if it (in sludge) is pumpedor travels even as little as a few hundred feet. In contrast, themixer-flocculating system on a trailer is designed to properly activatethe polymer and go through the flocculation process for immediate use atthe point of application. The instant invention includes a completeflocculation system (including inline flocculation, a polymer feedsystem, a liquid caustic pump and all accessories) on a heavy dutyutility trailer.

The fifth step/stage in the invention process uses a sludge retriever toseparate the dried sludge layer from the sand in the sand bed. Thesludge retriever is designed to fit any adequately rated (front-end)loader and is powered by the hydraulic system of the loader. Easilyoperated by one person, the retriever's rotary drum of the efficientlybreaks up (chops) solid waste and propels it into a hopper. The sludgeis chopped into very small granular particles, enhancing transportationand handling cost. The unique combing action of the rotating drum(preferably having 3-inch adjustable tines) not only removes sludgewithout significantly disturbing the filtering sand, it also levels thebed surface to promote uniform drying. Each bucketload of sludge removedby the sludge retriever usually will only yield an insignificant amountof sand for precision sludge clean-up. The sludge retriever (automated)makes sludge removal and drying bed preparation a one-man, one-machineoperation. It also levels and aerates the sand bed for the next pouringof sewage into the sand bed.

The sludge removal attachment is capable of removing dried wastewatersludge from sand drying beds. The implement is also capable of beingattached to the front end loader. The mechanism has, for example, a twocubic yard bucket, constructed of 1/4 inch steel, and a shaft-typerotary drum having multiple three inch tines. The unit is furnished withan expanded steel cover for the rotor and bucket. Rotor end plates are1/2 inch steel minimum. The rotary action of the drum accomplishesseveral functions. First, it removes the sludge layer. Second, itsimultaneously levels the surface of the drying bed. Third, by reversingthe direction of the rotary drum, the sand bed can be aerated to a depthof three inches. Basically, sludge is removed by passing the unit overthe drying bed and sweeping up the dried sludge.

Typical specifications are as follows: The overall width of themechanism best not exceed 82 inch and the working width best not exceed74 inch. The drive motor can best be 8 HP minimum and bi-directional.The drive chain should be #60 HD and the unit should be furnished with aclosed metal cover for the chain drive. Hydraulic requirements for theunit should be 9 to 14 GPM at 1800 to 2200 PSI. The total weight can be1000 pounds. The rotor construction can be shaft type with multi 3"tines. The hydraulic drive motor can be bi-directional 8-10 HP. Thedrive chain can be #60 HD. The rated capacity can be 3/4 yds. lightmaterial. The rotor adjustment can be cam type 1"-3".

Alternatively, the sludge removal attachment (retriever) is capable ofremoving air-dried wastewater sludge from the sand bed. The unit is abucket or scoop type device. Sludge is removed by passing the unit overthe drying bed and scooping up the dried sludge.

Safety features typically include: an expanded metal cover for the rotorand bucket; a metal cover for the chain drive; 3/8" steel rotor support;and pinch points identified.

The benefits achieved by the sludge retriever include:

(A) Ending expensive or greatly reducing manual labor;

(B) Sand removal is minimal;

(C) Leveling bed surface to promote uniform drying;

(D) Aeration of the sand; and

(E) One-man, one-machine operation.

The optional sixth step/stage in the invention process uses a sewagethickening or concentration unit which is a pneumatic dewatering deviceor tube. Liquid can be removed from the sewage by passing theliquid/solid through a screen causing liquid discharge. The screen isconstantly cleaned by air injection. This process can be repeated overand over producing a true inline thickening process, that is theconcentration of solids in the flowing sewage. The inline sewagedewatering device can be used before the first step in the inventionprocess or between the first and second steps or the second and thirdsteps or the third and fourth steps of the process.

Besides the dewatering of sewage, the pneumatic dewatering device ortube can be used to concentrate or deliquid (or dewater) solutions ofany liquid containing solids. The solutions which can be concentratedcan be, for example, in the chemical, pharmaceutical, mining, papermaking, etc., industries. The device is useful with processes whereinfluents, effluents, liquid bylines, etc., need to have the solidscontent increased.

Basically, in the invention dewatering process, the inline pneumaticdewatering tube allows part of the liquid in the flowing sewage to exitthe side of the vessel through a reinforced membrane wall. As the sewageflow passes through the vessel in a vertical direction, static headoccurs. Liquid will exit through the membrane wall until it clogs. Toprevent this from happening, air nozzles spray on every square inch ofthe wall in alternating patterns. The result is a cleaning and pulsingprocess causing the liquid/solid content to move in and out of contactwith the wall. Air to the system is supplied by a compressor or othermeans. The outer hub (common air supply) is fabricated in ringed cellsstarting at the bottom and are evenly spaced to the top of the hub.These cells maintain a specified PSI due to inlet and outlet checkvalves. Ball valves can regulate the amount of air passed to and througheach cell. Liquid exiting the membrane wall will free fall into thecenter between the wall and hub and exit the system. The discharging ofliquid can continue in series to obtain the desired thickening ofsolids.

The benefits achieved by the sludge thickener include: that thisextraction process is non-mechanical; that the inline pneumaticdewatering tube will not clog; and the inline thickening process.

The invention also includes the novel polymer mixing-feeding device ofthe invention.

The invention further includes the mixing-flocculating system of theinvention. Such apparatus for mixing and flocculating fluids containingsuspended solids includes conduit means for conducting the fluid to anoutlet in the conduit means, a vertical drop section in the conduitmeans, a horizontal section in the conduit means extending from thevertical drop section, a vertical rise section in the conduit meansextending from the horizontal section, a horizontal recycle section insaid conduit means extending from said vertical rise section to saidvertical drop section. A movable, nonflexible baffle plate is pivotallymounted on one end in the vertical drop section at or near the topportion of the intersection between the vertical drop section and thehorizontal recycle section. The pivotal, movable baffle plate is adoptedto constrict in a variable manner, at such location, the internaldiameter of the vertical drop section. A set of at least one nonflexiblebaffle located on the bottom internal surface of and a set of at leastone nonflexible baffle located on the top internal surface of thehorizontal section. The sets of nonflexible baffles are positioned inrelation to each other so as to be in alternating sequence. Preferablyat least one nonflexible baffle is located on the top internal surfaceof the horizontal recycle section. Preferably a nonflexible baffle islocated on the internal wall of the vertical rise section opposite ofthe horizontal recycle section so as to be at or near the lower portionof the intersection of the vertical rise section and the horizontalrecycle section. Preferably a nonflexible baffle is located on theinternal wall of the vertical drop section opposite of and below theintersection of the vertical drop section.

Also preferably means for introducing a floc producing agent into thefluid or liquid in the conduit means upstream of the vertical dropsection. Preferably the means introducing a floc-producing agentcomprises a plurality of injector jets spaced around the periphery ofthe conduit means upstream from the vertical drop section.

The invention also includes a combination of the mixing flocculatingdevice of the invention mounted on the bed of a truck or on a trailer. Apolymer mixing system and a means for adjusting the pH of the sewage arealso preferably mounted on the trailer. The polymer mixing system isused for preparing an activated polymer solution and injecting theactivated polymer solution into the inflow line of themixing-flocculating device. A generator can also be mounted on thetrailer to provide electrical power to operate the polymer mixing systemand the means for adjusting the pH of the sewage.

The invention also involves an improved sand cell for the dewatering ofsewage composed of water and particulate solids. A grid having openvertical passageways is positioned horizontally in the sand layer in thesand cell. Preferably the grid has a honeycomb or similar shape.Preferably the grid is composed of high density polyethylene plastic.

The invention also includes the pneumatic dewatering (deliquiding)device or tube of the invention.

The pneumatic deliquiding tube, which is adopted for use in the verticalorientation of the central axis of said deliquiding tube, includes acylindrical shell, a cylindrical tubular filter positioned inside of thecylindrical shell, and two cylindrical blocks, each of which is affixedon the outer portion of one end to an end of the cylindrical shell andon the inner portion to of such end to the corresponding end of thecylindrical shell. The blocks have a central passageway whichcorresponds to the interior of the cylindrical filter. There is aplurality of passageways in the cylindrical shell which traverseentirely around said cylindrical shell. There are at least two manifoldmeans oriented parallel or at an acute angle to the central axis of thedeliquifying tube. The manifolds are located external to the cylindricalshell. Each of the manifolds communicates by means of conduits to everyother of the passageways (that is, in an alternative sequence). At leastone of the manifolds communicates with passageways other than thepassageways with which at least one other manifold communicates. Aplurality of air jets is located on the inner wall of the cylindricalwall. Each of the passageways has at least two of the air jetscommunicating therewith. The manifolds are adopted to be connected to asource of pressurized gas. There is means for controlling the flow ofpressurized gas so that the pressurized gas is delivered in short phasesor bursts in a manner alternating between the manifolds whichcommunicate with different alternative arrays of the passageways. Thepressurized air exits from the air jets against the external surface ofthe cylindrical filter in the alternating manner. At least one channelis in at least one of the blocks. Such channel communicate from thespace between the cylindrical shell and the cylindrical shell to theexterior. The pneumatic deliquiding tank can be constructed so that thecylindrical shell and the cylindrical filter is segmented with one ofthe blocks between each of the segments--see FIG. 12.

The sludge thickener has the ability to dewater (deliquid) any solutioncontaining solids. The device extracts liquid from a liquid/solid bypassing the liquid/solid through a screen causing liquid discharge. Thescreen is constantly cleaned by air injection.

Modifications and changes made to this sludge treatment process can beeffected without departing from the scope or spirit of the presentinvention. For example, a sand-cell media (grid) in which the shape ofthe individual cells does not result in a honeycomb formation may beused. Also, the embodiments of this sludge treatment process which areillustrated as follows have been shown only by way of example and shouldnot be taken to limit the scope of the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic diagraph of the steps or stages in the inventionprocess/method;

FIG. 2 is a side, elevational view, partially cut-away, of the polymermixing-feeding device of the invention;

FIG. 3 is a perspective view, partially cut-away, of the apparatus forflocculating fluids containing solids, along with polymer injectors, ofU.S. Pat. No. 5,248,416.

FIG. 4 is a side elevational view of the mixing-flocculating system on atrailer;

FIG. 5 is a side, cross-sectional view of the mixing-flocculating unit;

FIG. 6 is a side, elevational view of the mixing-flocculating system ona trailer including a barrel, a dip tube, a motor and a control valve;

FIG. 7 is a perspective view of a vertical cross-section of the sandfilter set-up of the invention including a layer of sand, a sand-cellmedia in the sand layer, a porous (stones or pebbles) layer, non-porouspipes having holes therein and a non-porous bottom layer;

FIG. 8 is a perspective view of a vertical cross-section of the sandfilter set-up of the invention shown in FIG. 7; having holes and anon-porous layer;

FIG. 9 is an elevational view of the sand-cell media having a honeycombformation;

FIG. 10 is an elevational view of the sand-cell media (in honeycombformation) and surrounding sand layer showing the forces impacting thesides of a single sand-cell when the wheel of a loader or other loadingequipment is on the sand surface above it;

FIG. 11 is a side, elevational view of the sludge retriever operating ontop of a sludge drying sand bed which includes sand-cell media;

FIG. 12 is a longitudinal, partial cross-sectional view of oneembodiment of the pneumatic dewatering device of the invention; and

FIG. 13 is a longitudinal, partial cross-sectional view of anotherembodiment of the pneumatic dewatering device of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 describes the five step/stage process of the invention describedin FIG. 1. Sewage 40 is obtained from a primary sewage treatment systemwhich is or includes a filtering step to remove large objects, grit andthe like and a sedimentation tank step to remove suspended settleablesolids. Activated polymer solution from inline polymer mixer 41 isinjected into sewage 40 to aid in flocculation. The sewage 40 then movesinto inline mixing-and-flocculating unit 42 wherein the sewage is mixedand flocculated to enhance chemically induced liquid-solids separation.The treated sewage exiting from mixing-and-flocculating unit 42 issubjected to chemical pH adjustment 43 by the addition thereto by a basesuch as lime or caustic (potassium hydroxide or sodium hydroxide). ThepH of the sewage is adjusted into the basic pH range or to a higherbasic pH. The sewage is then poured onto sand bed 44 which contains asupport grid therein. The larger insoluble solids and flocks in thesewage collect on the top of sand bed 44 and the water in the sewagepasses/filters through sand bed 44. Once the solids and flocks locatedon top of sand bed 44 dry, a layer of dried sludge pieces is obtained ontop of sand bed 44. The dried sludge pieces are then removed in sludgeretrieval step 45 to provide dried sludge 46.

With regard to the first step of the invention process, that is, polymermixing and injecting device (see FIG. 1) is more fully shown in FIG. 2.The polymer mixing-feeding (injecting) (165) system is an integratedequipment package which automatically meters, activates, dilutes andfeeds liquid polymer and water. (See FIGS. 2 and 6.) Concentratedpolymer and water are blended in a complete high energy chamber.

The prepared solution via tube (166) exits the original chamber (167)through the top of the vessel (168). It then re-enters an outerretention chamber (169) and exits the chamber (169) via tube (170) atthe bottom of the vessel to the polymer injectors. A round access plate(171) is fabricated in the bottom of the primary chamber (167) forrepair and service. The chamber (167) can be constructed of polyvinylchlorides, stainless steel or any other suitable material. Polymer froma source not shown is transported in tube (172) by means of meteringpump (173). Unit (173) mixes water with the polymer. The polymer isinjected into the chamber (167) through a tube (172) passed through thetop of the chamber (167). The tube (172) is designed to be adjustable inlength giving variations in depth or placing the polymer closer to theaspirator or mixing energy. At the end of the tube (172), a springloaded check valve (174) allows polymer to spray into the mixing area ina thin filming process (182). Energy for polymer activation is createdby a 5/8 inch or any size stainless steel hollow shaft (175) which atthe end of the shaft is a polyvinyl chloride or stainless steel 4-wayaspirator (176). With the aspirator turning at 3,450 rpm, a tremendousvacuum occurs drawing free air down the hollow shaft (175) into thechamber (167). This process causes high energy mixing. The stainlesssteel shaft (175) is driven by a hollow core motor (177). The motor(177) and shaft (175) are attached by a coupler (176). The 5/8 inch orany size shaft (177) with aspirator (176) is placed inside the chamber(176) and that chamber (176) is made water tight with exteriormechanical seals (178). Inline check (179) and ball valves (180) areinstalled on the top or inlet side of the motor (177). These valves(180) can regulate the amount of air passed through the hollow shaft(175) to the mixing chamber (176). The one way directional flow checkvalve (179) is used to prevent liquid from exiting through the aspirator(176) and shaft (175) when the motor (177) is in the off position. Themixer has a brass solenoid valve for on/off control of dilution watersupply (not shown), and a rotameter-type flow indicator (181) equippedwith integral rate-adjusting valve. Water is supplied to primary chamber(167) via tube (183). The flow indicator is machined acrylic and hasvalve stop and guided float. Water flow rate is adjustable 0 to 500USGPH. Water supply input and stock solution output fittings are 0 to500 FNPT. The drive motor (177) of the unit is powered by a 2500 wattgenerator producing 12OV-15 amps. The generator (not shown) is mountedto the trailer and becomes a permanent fixture of the transportablesystem.

With regard to the second step of the invention process, that is, inlinemixing and flocculating (see FIG. 1), the following mixer-flocculatingsystem is constructed: Onto the bed of a trailer (110), themixer-flocculating system (101) is secured. (See FIG. 4.) Part of themixer-flocculating system is a mixer-flocculator unit (80). Sewageenters pipe (102) the mixing-flocculator unit (80) through an elbow(103). The elbow (103) is attached to a vertical inlet pipe segment(104) which is, in turn, attached to another elbow (103). This latterelbow (103) has a flange (82) which is attached to a flange on the endof a downflow segment (105). The downflow segment (105) continues into ahorizontal bottomflow segment (106). A recycle segment (111) contactsthe downflow segment (105). An electrical control-drive unit (88) turnsa threadedly adjustable rod (88a) extending through the wall of thedevice to contact the top of adjustable baffleplate (87). Baffleplate(87) is pivotally attached (87a) to the side of to the downflow segment(105) near the top where the downflow segment (105) and recycle segment(111) intersect. The adjustable, nonflexible baffleplate (87) is locatedat an angle (which can be readily changed) within the downflow segment(105). (See FIG. 5.) The electrical control-drive unit (88) can,instead, be a manual control (of the angle of the adjustablebaffleplate), such as, manually turning the rod (88a). The other end ofthe recycle segment (111) and the other end of the bottomflow segment(106) are joined to openings in a upflow segment (107). At one end ofthe upflow segment (107) is a flange (82) which is attached to a flange(82a) at one end of an elbow (103). The other end of this elbow (103) isattached to a vertical, exit pipe segment (108). Attached to the otherend of the vertical, exit pipe segment (108) is another elbow (103)through which the sewage exits (109).

Running into the elbow (103) which is attached both to the verticalinlet pipe segment (104) and the downflow segment (105) are polymer orflocculant injection lines (84). Attached to the other end of thesepolymer or flocculant injection lines (84) are a manifold (85), a quickconnect (86), a motor (115) and a control valve (114). (See FIG. 6.) Adip tube (113) runs from the control valve (114) into a barrel (112)resting on the trailer (110). Preferably the polymer mixing andinjecting apparatus of FIG. 13 is used to provide the activated polymersolution to barrel 112.

Sewage enters an elbow (103) and runs through the vertical inlet pipesegment (104). It then passes through another elbow (103) into thedownflow segment (105). As the sewage/flow passes into the downflowsegment (105), it passes through a 45 degree angle. This area is calledmixing zone 1 (83). As the sewage/flow runs through the downflow segment(105), it encounters an adjustable baffleplate (87), which is positionedat an angle. The adjustable baffleplate (87) restricts the vessel's flowby about 50 to about 80 percent, thus increasing the original flowvelocity by as much as 600 percent. Then, the sewage/flow is fanned inone direction--towards the bottomflow segment (106). A fixed baffle(90), which restricts typically 40 percent of the vessel's size, ispositioned in the downflow segment and serves to oppositely direct andfan the passing sewage/flow. The area between the adjustable baffleplateand the fixed baffle is called mixing zone 2 (89). Then, the sewage/flowis directed into a 45 degree round angle into the bottomflow segment(106). Positioned within the bottomflow segment are at least two(preferably, a number of) fixed, horizontal baffles (92), thepositioning of which cause the sewage/flow to pass under and over andunder these fixed, horizontal baffles (92) in a serpentine flow pattern,thereby reducing the flow velocity. This area is called mixing zone 3(93). The sewage/flow, then, enters the upflow segment (107) in a 45degree round angle which causes the sewage/flow to move in a spiralingpattern. Positioned in the upflow segment (107) is (at least one) fixedvertical baffle (96). Mixing zone 5 is in the exit end of upflow pipe107 where it bends to the horizontal. Before the sewage/flow exits themixer-flocculator unit (80), before it enters an elbow (103) and thevertical exit pipe segment (108), it passes a horizontal pipe/recyclesegment (111) which causes a portion of the sewage/flow to divertthrough this line, because of the pressure drop caused by the adjustableinlet baffle (87) placed at an angle. The bypass velocity may beincreased, if the size of the pipe is increased and with baffleadjustments. Also before the sewage/flow exits the mixer-flocculatorunit (80), before it enters an elbow (103) and the vertical exit pipesegment (108), but after it passes the horizontal pipe/recycle segment(111), it passes through a 45 degree angle. This area is called mixingzone 4 (99). Recycle segment (111) has a smaller diameter than the restof the pipes of the unit.

A drainage plug (91) is present in the downflow segment (105), close towhere the sewage/flow enters the bottomflow segment (106). A flush plug(95) is present in the upflow segment (107) close to where it joinstogether with the bottomflow segment (106).

Model RF6 of the mixing and flocculating unit 80 os basically shown inFIG. 5. Note the two non-flexible baffles 92 located in the bottom ofbottomflow segment 106. The results of tests using Model RF6 indewatering test are given below in Table 1 and 2.

                  TABLE 1                                                         ______________________________________                                        MIXING ZONES                                                                  (Velocity versus feet per second)                                             G.P.M.  ZONE 1   ZONE 2   ZONE 3 ZONE 4 ZONE 5                                ______________________________________                                        A)  100     1.28     5.04   2.89   8.68   1.28                                B)  150     1.92     7.56   3.83   13.10  1.92                                C)  200     2.57     10.10  4.44   17.4   2.57                                ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________                          Baffle Plate                                                        Emulsion                                                                           Polymer                                                                            Position                                                       Sludge                                                                             Polymer                                                                            Solution                                                                           (% of      Filtrate                                                                           Dried Sludge                            Velocity                                                                             Con. Conc.                                                                              Conc.                                                                              Vessel                                                                              Floc Size                                                                          Conc.                                                                              (% and                                  (G.P.M.)                                                                             (% T.S.)                                                                           (Neat)                                                                             (%)  Dia)  (SML)                                                                              (% T.S.)                                                                           Time)                                   __________________________________________________________________________    A)                                                                              100  2%   55%  .25  .70   L    0    6 hrs.-14%                                                                    24 hrs.-24%                                                                   48 hrs.-30%                                                                   72 hrs.-47%                                                                   168 hrs.-60%                            B)                                                                              150  2%   55%  .25  .65   L    0    same                                    C)                                                                              200  2%   55%  .25  .60   M    0    same                                    __________________________________________________________________________

Model RF8 is similar to Model RF6 except it has a larger flow capacityand only has one nonflexible baffle 92 in the bottom of flow segment 106(located between the two baffles 92 in the top thereof). The results oftests using Model RF8 in dewatering tests are given below in Tables 3and 4.

                  TABLE 3                                                         ______________________________________                                        MIXING ZONES                                                                  (Velocity versus feet per second)                                             G.P.M.  ZONE 1   ZONE 2   ZONE 3 ZONE 4 ZONE 5                                ______________________________________                                        A)  200     1.28     5.04   2.89   8.68   1.28                                B)  300     1.92     7.56   3.83   13.10  1.92                                C)  400     2.57     10.10  4.44   17.4   2.57                                D)  500     3.31     12.60  5.55   21.7   3.21                                E)  600     3.85     15.10  6.66   28.0   3.85                                F)  700     4.49     17.60  7.77   30.4   4.49                                ______________________________________                                    

                                      TABLE 4                                     __________________________________________________________________________                          Baffle Plate                                                        Emulsion                                                                           Polymer                                                                            Position                                                       Sludge                                                                             Polymer                                                                            Solution                                                                           (% of      Filtrate                                                                           Dried Sludge                            Velocity                                                                             Con. Conc.                                                                              Conc.                                                                              Vessel                                                                              Floc Size                                                                          Conc.                                                                              (% and                                  (G.P.M.)                                                                             (% T.S.)                                                                           (Neat)                                                                             (%)  Dia)  (SML)                                                                              (% T.S.)                                                                           Time)                                   __________________________________________________________________________    A)                                                                              200  2%   55%  .25  .70   L    0    6 hrs.-12%                                                                    24 hrs.-22%                                                                   48 hrs.-35%                                                                   72 hrs.-45%                                                                   168 hrs.-65%                            B)                                                                              300  2%   55%  25   .65   L    0    same                                    C)                                                                              400  2%   55%  .25  .60   M    0    same                                    D)                                                                              500  2%   55%  .30  .55   S    0    same                                    E)                                                                              600  2%   55%  .50  .50   S    0    same                                    F)                                                                              700  2%   55%  .55  .50   S    0    same                                    __________________________________________________________________________

The sewage apparatus of U.S. Pat. No. 5,248,416 (Howard) is shown inFIG. 1. In the apparatus of Howard, incoming liquid containing solidsand recirculated liquid containing solids and flock fills the entireapparatus, including pipe 229. The velocity going into the system is thesame as that exiting the system. The path of the flow of material isdown conduit 217, through bottom conduit 220, up conduit 224, and thensplit so as to be partly recycled through the top pie (229) and partlypassed on out conduit 224, without any meaningful restrictions. Item 220is a moveable flutter or ledge and items 229a are fabricated rubbertumblers which bend with the flow and, thus, offer little or norestrictions in the flow paths. Moveable 220 is located in down flowconduit 217 at the lower intersection point of recycle conduit 229 anddown flow conduit 217. Through testing of the Howard system, applicanthas found that the Howard system is not very effective in achieving itsstated purpose and in solving its stated prior art problem.

In contrast, the improvements of the instant invention include amixer-flocculator unit having an adjustable baffleplate placed at anangle to the direction of flow of the incoming sewage (containing, forexample, 1/2 to 8 percent of solids). The baffle plate restricts theflow area in downflow pipe segment 106 just before the intersection withrecycle pipe segment 111 by about 50 to about 80 percent. Thiscross-sectional area adjustment process can increase the original flowvelocity by as much as 600 percent or more. The pattern of flow of thecombination of the incoming material and the recycle material, then, ismoved in one direction. Thereafter, flowing liquid is oppositelydirected and fanned by a fixed, nonflexible baffle which restricts 40percent or so of the internal size (cross sectional area) of the pipe.Then, the liquid flow is directed into a 45 degree round angle whichcauses the liquid flow to turn and pass under and over and under fixed,nonflexible baffles in a serpentine flow pattern, thereby furtherreducing the velocity of flow in the pipe. Thereafter, the liquid flowenters a 45 degree round angle which causes the flow to move upward in aspiraling pattern. The liquid flow, then, comes in contact with a fixed,nonflexible baffle. Such baffle is located across from the entrance to aside or recycle pipe. As the upward liquid flow reaches such baffle andside horizontal recycle pipe, a portion of it to divert through thisline by the action of such baffle and by the pressure drop caused by theadjustable inlet baffle plate in the down flow pipe segment 106. Theinternal diameter of recycle pipe 111 is less than the internal diameterof down flow pipe 105 or upward flow pipe 107. The bypass velocity inthe recycle pipe can be increased by decreasing the size of the pipeand/or by adjusting the baffle. This recycle system allows the continuedsize growth of the floc.

Preferably the mixer-flocculator unit will have multiple injector portsat the influent end of the mixer, through which the activated polymersolution can be injected into the liquid-sludge slurry flow stream. Theactivated polymer and sludge will then be quickly but gently mixed bybaffling energy dispersing action. The mixing action promotes large flocgrowth. A portion of the flocculated sludge, then, is re-circulated intothe influent stream by a pressure drop zone to advance and increase theefficiency of the mixing-flocculating process. The device can befabricated utilizing corrosion free polyvinyl chloride components,stainless steel, concrete, fiberglass, wood or any other suitable metalor other material. The interior baffles can be fabricated from polyvinylchloride, stainless steel, concrete, fiberglass, wood or any othersuitable metal or other material.

With regard to the third step of the inventive process, that is, achemical induced pH adjustment of the sewage exiting themixer-flocculating system (101), the following is included: As theliquid/solids content exits the inline mixer-flocculator unit (80), anelectronic or gear driven diaphragm pump (not shown) pumps liquidcaustic or lime into the discharge line for example, 102, 108, 109,etc.) of the flocculator-mixer unit (80). The pH of the sludge isincreased to 12 by the chemical additive (base). The pH of the sludgewill remain at 12 for 72 hours, and, during this period of time, thetemperature will reach 52° C. and will remain at that temperature for atleast 12 hours. At the end of the 72 hour period during which the pH ofthe sludge is above 12, the sludge can be air dried to achieve a percentsolids of greater than 50 percent. The liquid caustic or lime pump ispresent on the transportable dewatering trailer (110) with themixer-flocculating system (101) and the polymer feed system and, thus,is easily transported.

With regard to the fourth step of the invention process (see FIG. 1),enclosure 49 contains sand bed 44. Onto a layer of non-porous material(50), e.g., concrete, a layer of porous material (53) is positioned.Porous material (53) is used as a filter media and usually stone,crushed rock, ceramic shapes, slag and plastics of 1 to 6 inches,practically 2 to 4 inches, in size are used. Stones or pebbles arepreferred. At least one--usually more than one--projection of porousmaterial (54) extends from the porous layer (53) into the layer ofnon-porous material (50). Embedded in each projection channels (48) inporous material (54) is at least one non-porous pipe (55) having atleast one hole (56) into which liquid can drain. A layer of sand (57) ispositioned above the layer of porous material (53). The sand-cell mediasections (65) are positioned above this layer of sand (57). Sand islocated in passageways 59 in sand cell grid (65). Above each sand-cellmedia section (65) is placed a layer of sand (61). This layer of sand(61) is usually, though not necessarily, at least six inches in depth.

Walls (51) surround on all four sides of an area having one or moresand-cell media sections (65)--on wall 51 is shorter to allow a frontloader or the like into the enclosure. Each surrounding, dividing wall(51) extends upward from one or more footing supports (52) which arepositioned, at least partially, in the layer of non-porous material(50). The top of each dividing wall (51) extends above the layer of sand(61) overlaying the sand-cell media section(s). On the top of eachdividing wall (51) which runs between two enclosure areas havingsand-cell media sections (65) is portable nozzle (62) which is used topour sewage into the enclosures.

Each sand-cell media section (65) is made up of one or more sand-cells(58) having the same shape and size. Typically, the sand-cell mediasection is made up of honeycomb-shaped sand-cells (58) which are joinedtogether in a honeycomb formation (i.e., each sand-cell which is not inan outer layer, where it intersects (59) another sand-cell, itintersects three other sand-cells). A channel (59) runs through theinterior of each sand-cell.

Sewage is poured through the channel (62) into one or more enclosures 49for sand beds 44. The liquid permeates the outer sand layer, flowsthrough the sand in the channels (59) in the grid 65 in the centers ofthe sand-cells, permeates the layer of sand beneath the sand-cell media,and permeates the pebble layer beneath that layer, leaving the collectedsludge solids to dry from the sun and air.

With regard to the fifth of the invention process (see FIG. 1), a sludgeretriever (125) is used to separate the dried sludge layer (134) fromthe sand (61) in the sand bed (44). (See FIG. 11.) An upper pivoted arm(130) is attached to a front-end loader, as is a lower pivoted arm(129). The other end of each of these pivoted arms is attached to a twocubic yard bucket/hopper (133). The lower side (137) of thebucket/hopper (133) slides along the sandbed slightly above or on thelayer of dried sludge (134) being retrieved. The lower, front end (138)of this bucket/hopper (133) is upwardly slanted relative to the rest ofthe lower end. At the lower back end of the bucket/hopper is attached arotary drum (135) including a shaft (126) around which a rotary (128),from which multiple raw of three inch tines/teeth (127) project, turns.As the rotary drum (135) turns (clockwise), pieces of dried sludge (134)and minimal amounts of sand (61) are tossed into the bucket/hopper(133). An arm (132) is attached to a ball pivot (131) which has a shortarm (139) welded onto the end of ball joint (131). Ball joint (131) ismoved up or down in vertical slot (140) in the side of retriever (125)and moved and bolted into one of the three short horizontal slots (141),whereby shaft (126) is moved up or down to the desired position. Thisarrangement (not shown) is repeated on the other side of the retriever(125). In this manner, the height position of shaft (126) can beadjusted and accordingly the distance that vanes (127) extend belowlower side (137) of retriever (125). As typically shown in FIG. 11, vane(127) extension levels of 1 inch, 2 inches and 3 inches are indicated bythe marks "1", "2" and "3", respectively. The one inch level is usuallyused to chop up the dried sludge. The 2 inch level is shown in operationin FIG. 11. The three inch level is used, when the rotation direction ofrotary (128) is reversed, to aerate the sand after the dried sludge hasbeen removed. Air flow grill or filter (136) is located in the topsurface of bucket (133) near its front.

With regard to the optional (sixth) step of the invention, that is,dewatering the sewage using an inline vertically-oriented, pneumaticdewatering tube (164) between steps (a) and (b) or (b) and (c) or (c)and (d), or before step (a), see FIG. 12. A cylindrical-shaped screenfilter (150) reinforcing ribs (151), usually composed of stainlesssteel. Rim rings (159) connect the circular-shaped screen filter (150)with a rim block (163). Running through the rim (163) are water exitpassageways (158). The flanged ends of cylindrical shell (153) arebolted (161) together with rim block (163). In this shell (153) areperipheral air chambers (154) which traverse the entire circumference ofshell (153). One end of the water exit passageways (158) opens into thearea in between the shell (153) and filter (151). Positioned in thisarea are staggered, pressurized air jets (152) communicating with airchambers (154). Manifolds (155) are positioned outside of shell (153)and communicate with every other circular air chamber (154), and henceto every other bank of pressurized air jets (152).

Use of the pneumatic dewatering device or tube (164) involves conducting(160) the sewage into the central tube-shaped filter where solids in thesewage are caught on the filter (150) and part of the water in thesewage passes through the filter (150). Air under pressure is blown fromstaggered, high pressure air jets (152) against the outer surface of thefilter (150) to dislodge the solids collected on the inner surface ofthe filter (150). The blowing air jets (152) are alternated in on-offsequences in order to continuously provide regions of the filter for thewater to come through unimpeded by blowing pressurized air.

In an alternate form of the invention (see FIG. 13, as opposed to thatwhich is portrayed in FIG. 12), there is not a liquid exit passageway(158) running through each rim (163) through which liquid sewage isdispelled (157). Rather, there is a channel (162) for sewage to flowthrough the rim (163) from one section to another and then out thebottom.

LIST OF PARTS NUMBERS

In connection with the figures, the following list of the names of theparts of the instant invention are noted:

    ______________________________________                                        Numbers                                                                              Parts, Etc.                                                            ______________________________________                                        40     sewage;                                                                41     inline polymer mixer;                                                  42     inline mixing and flocculating unit;                                   43     chemical pH adjustment;                                                44     sand bed;                                                              45     sludge retrieval;                                                      46     sludge;                                                                48     channels;                                                              49     sand bed enclosures;                                                   50     non-porous layer;                                                      51     dividing wall;                                                         52     support upon which dividing wall is positioned;                        53     porous layer positioned directly above non-porous                             layer (50);                                                            54     projection of porous layer (54);                                       55     non-porous pipe;                                                       56     hole in non-porous pipe (56);                                          57     layer of sand underlaying sand-cell media section;                     58     single sand-cell;                                                      59     channel running through interior of single sand-cell;                  60     point of intersection of 4 individual sand-cells;                      61     layer of sand overlaying sand-cell media section;                      62     channel into which sludge is poured                                    63     loader or other loading equipment;                                     64     wheel of loader or other loading equipment;                            65     sand-cell media section;                                               80     mixer-flocculator unit;                                                81     input conduit (influent end of mixer);                                 82     flanges;                                                               82a    flange;                                                                83     mixing zone 1;                                                         84     polymer or flocculant injection lines;                                 85     manifold;                                                              86     quick connect;                                                         87     adjustable baffleplate placed at an angle;                             87a    pivot attachment;                                                      88     electrical unit;                                                       88a    threadedly adjustable rod;                                             89     mixing zone 2;                                                         90     fixed, vertical baffle;                                                91     drainage plug;                                                         92     fixed, horizontal baffles;                                             93     mixing zone 3;                                                         94     walls;                                                                 95     flush plug;                                                            96     fixed, vertical baffle;                                                97     mixing zone 5;                                                         98     recirculation baffles;                                                 99     mixing zone 4;                                                         100    output conduit;                                                        101    mixer-flocculating system;                                             102    liquid in;                                                             103    elbows;                                                                104    vertical inlet pipe segment;                                           105    downflow segment;                                                      106    bottomflow segment;                                                    107    upflow segment;                                                        108    vertical exit pipe segment;                                            109    liquid out;                                                            110    transportable dewatering trailer;                                      111    recycle segment;                                                       112    barrel;                                                                113    dip tube;                                                              114    motor;                                                                 115    control valve;                                                         125    sludge retriever;                                                      126    shaft;                                                                 127    multiple 3 inch tines/teeth;                                           128    rotary;                                                                129    lower pivoted arm attaching sludge retriever to                               front-end loader;                                                      130    upper pivoted arm attaching sludge retriever to                               front-end loader;                                                      131    ball pivot;                                                            132    arm;                                                                   133    two cubic yard bucket/hopper;                                          134    dried sludge;                                                          135    rotary drum;                                                           136    air flow grill or filter;                                              137    lower side;                                                            138    front end;                                                             139    arm;                                                                   140    vertical, slot;                                                        141    show horizontal slots;                                                 150    screen filter;                                                         151    rib;                                                                   152    high pressure air jet;                                                 153    wall;                                                                  154    circular air chamber;                                                  155    manifold;                                                              156    pressurized air in;                                                    157    liquid sewage out;                                                     158    liquid exit ring;                                                      159    rim ring;                                                              160    passageway for sewage;                                                 161    bolt;                                                                  162    channel for sewage;                                                    163    rim;                                                                   164    inline pneumatic dewatering tube;                                      165    polymer mixing-feeding system;                                         166    tube;                                                                  167    inner chamber;                                                         168    vessel;                                                                169    retention chamber;                                                     170    exit tube;                                                             171    access plate;                                                          172    tube;                                                                  173    water-polymer mixing unit;                                             174    check valve;                                                           175    hollow shaft;                                                          176    aspirator;                                                             177    motor;                                                                 178    seal;                                                                  179    check valve;                                                           180    ball valve;                                                            181    flow indicator;                                                        182    filming process; and                                                   183    tube.                                                                  ______________________________________                                    

In connection with the figures, the following list of the names of theparts of a prior art invention [U.S. Pat. No. 5,248,416 (Howard)] arenoted:

    ______________________________________                                        212       upper right hand conduit/system input;                              214       multiple polymer ejectors;                                          217       conduit;                                                            220       moveable flutter or ledge;                                          222       conduit;                                                            222a      conduit;                                                            224       conduit;                                                            226       output conduit/system output;                                       229       recirculating conduit;                                              229a      pivotal flaps on recirculating conduit; and                         230       support bracing.                                                    ______________________________________                                    

What is claimed is:
 1. Apparatus for mixing and flocculating fluidscontaining suspended solids comprising conduit means for conducting saidfluid to an outlet in said conduit means, a vertical drop section insaid conduit means, a horizontal section in said conduit means extendingfrom said vertical drop section, a vertical rise section in said conduitmeans extending from said horizontal section, a horizontal recyclesection in said conduit means extending from said vertical rise sectionto said vertical drop section, a movable, nonflexible baffle platepivotally mounted on one end in said vertical drop section at or nearthe top portion of the intersection between said vertical drop sectionand said horizontal recycle section, said pivotal, movable baffle plateadopted to constrict in a variable manner, at such location, theinternal diameter of said vertical drop section, a set of at least onenonflexible baffle located on the bottom internal surface of and a setof at lest one nonflexible baffle located on the top internal surface ofsaid horizontal section, said sets of nonflexible baffles beingpositioned in relation to each other so as to be in alternatingsequence.
 2. The apparatus as claimed in claim 1 wherein at least onenonflexible baffle is located on the top internal surface of saidhorizontal recycle section.
 3. The apparatus as claimed in claim 2wherein a non-flexible baffle is located on the internal wall of saidvertical rise section opposite of said horizontal recycle section so asto be at or near the lower portion of the intersection of said verticalrise section and said horizontal recycle section.
 4. The apparatus asclaimed in claim 3 wherein a non-flexible baffle is located on theinternal wall of said vertical drop section opposite of and below theintersection of said vertical drop section.
 5. The apparatus as claimedin claim 1 wherein means for introducing a floc producing agent intosaid fluid or liquid in said conduit means upstream of said verticaldrop section.
 6. The apparatus as claimed in claim 1 wherein said meansintroducing a floc-producing agent comprises a plurality of injectorjets spaced around the periphery of said conduit means upstream fromsaid vertical drop section.
 7. A combination of the mixing andflocculating device of claim 1 mounted on the bed of a truck or on atrailer.
 8. The combination of claim 7 wherein a polymer mixing systemand a means for adjusting the pH of the sewage are also mounted on saidtrailer, said polymer mixing system preparing an activated polymersolution and injecting said activated polymer solution into the inflowline of said mixing-flocculating device.
 9. The combination of claim 7wherein a generator is also mounted on said trailer to provideelectrical power to operate said polymer mixing system and said meansfor adjusting the pH of the sewage.